1.Field of the Invention
This invention relates to a non-cariogenic composition and drink for preventing or at least inhibiting human dental caries induced by Streptococcus mutans and other cariogenic bacilli.
2. Description of the Prior Art
Dental caries is a disease of teeth of humans and animals, which is induced by the action of cariogenic oral bacilli. Among them, Streptococcus mutans is believed to be most important. It has, hitherto, been disclosed, for example, in Bergy's Manual of Determinative Bacteriology, page 504 (1974) that a relationship exists between dental caries and Streptococcus mutans, it being suggested that S. mutans is a similar microorganism to S. salivarius, even though S. mutans has not yet been extensively studied and compared with S. salivarius. Nowadays, however, S. mutans which produces dextran-like polysaccharides (hereinafter referred to as DPS) from sucrose, is clearly distinguished from S. salivarius which produces fructans from sucrose. Strains of S. mutans adhere to the surface of the teeth of humans and animals and form dental plaque which is solid and adhesive. The major portion of S. mutans in the oral cavity resides in the plaque and produces lactic acid which directly breaks down the teeth. Even though other oral bacilli also produce lactic acid, the lactic acid produced by S. mutans is not released but is accumulated on the surface of the teeth. Thus, for example, British Patent 1,375,866 discloses that the formation of pre-carious dental plaque is a pre-requisite for the development of dental caries and that glucosyltransferease is an important factor in the development of dental caries. It is said that the main constituents of insoluble and water-soluble DPS produced by S. mutans are high molecular weight polymers of glucose comprising respectively .alpha.(1-3) and .beta.(1-6) bondings (Guggenheim, Internat. Dent. J., 20:675-678, 1980).
There are known various other cariogenic microoranisms other than S. mutans. For example, it is well known that certain bacilli conventionally used for the preparation of yogurt, cheese and various other foodstuffs containing lactic acid-producing bacilli have cariogenic potential. For example British Patent 1,375,866 discloses that Lactobacillus acidophilus, L. casei and Streptococcus faecalis are well known aetiological factors. Oshima also reported that L. casei and L. helvetius used for yogurts commercially available in Japan induced dental caries (The Japanese Journal of Pedodontics, 16, 1. 161-169, 1978 in Japanese version). Even though the cariogenic potential of other cariogenic bacilli is not higher than that of S. mutans,for example, they intrude into dental caries already induced by S. mutans and reside there. In such a case, for example, lactic acid and acetic acid produced by them do harm to the structure of the teeth.
It is known to inhibit (as hereinbefore defined) dental caries induced by S. mutans by using dental vaccine. Thus, for example, said British Patent 1,375,866 discloses a dental vaccine comprising as antigen the whole cells of S. mutans Strain SSC having the same characteristics as the characteristics of S. mutans NTCT 10449 which is a well-recognized cariogenic wild type strain of S. mutans. However, it is said that the use of the whole cells (especially, the living whole cells) of cariogenic strains of S. mutans as antigen, can give rise to various undesired side effects such as allergic reaction and cross reaction with the heart muscle antigen, when administered to animals.
The use of bovine milk containing anti-S. mutans antibodies for inhibiting dental caries induced by S. mutans is also known (British Patent 1,505,513). However, the known bovine milk antibodies may not cannot inhibit S. mutans NCTC 10449, a well-recognized cariogenic strain of Human type S. mutans.
Apart from the known immunological methods, U.S. Patent 4,133,875 to Hillman (1979) discloses to control human dental caries induced by cariogenic strains of S. mutans by the use of non-virulent analogs of cariogenic S. mutans. Such a method is based upon the socalled bacterial interference which appears, in general, to involve a competitive and/or antibiotic reaction of the non-virulent strains viz. the effector strain on its pathogenic counterpart and that such a strain must be (a) non-virulent as itself and (b) able to successfully compete with its pathogenic counterpart (cf. U.S. Patent No. 4,133,875, column 3, lines 5-15).
Hillman discloses two effector strains, Streptococcus mutans JH140 (ATCC 31341) and JH145 (ATCC 31377), both isolated from streptomycin-resistant S. mutans BHT-2 (str.), followed by mutagensis. The biological characteristics of two effectors strains are, for example, as follows:
(a) inability to produce a detectable amount of lactic acid when incubated in the presence of glucose; PA1 (b) relatively better adhesion to hydroxypate than the parent strain; and PA1 (c) higher productivity of plaque than the parent strain when incubated in the presence of sucrose. PA1 (a) 93.9% of S. mutans of human origin were Human I type and the rest was Human II type; PA1 (b) all strains of rat origin were Rat type; PA1 (c) no S. mutans was isolated from mice and guinea pigs; and PA1 (d) all strains originating from hamsters and monkeys were Human I type. (Journal of Dental Health. Vol. 28, No. 2, pages 99-123, 1978 in Japanese version). PA1 (a) very complicated procedure is required for obtaining official license for the commercial production of vaccines, and moreover (b) in many countries of the world, it is, as a rule, extremely difficult or impossible to use the viable cells of mutant strains obtained by treating virullent microorganisms with mutagents, for example, as additive to foodstuffs. PA1 HS-1 (a), PA-1 (b), Ingbritt (c), NCTC 10449=ATCC 25175 (c), OMZ176 (d), P-4 (e), OMZ175(f), K1R (g) and RC-20 (b) (the serotypes are indicated in the brackets). PA1 (1) the characteristics of naturally-occuring Phase III-like strains are closely similar to the characteristics of Phase III mutant strains; PA1 (2) it appears that glucosyltransferase is the enzyme which directly participates in the induction of dental caries by S. mutans. PA1 (3) With respect to the enzymatic activities and agglutination titres, there is a difference between the inhibiting abilities of respective strains. PA1 4) The decomposition spectra of sugars of Phase III like (and Phase III) strains are broader than the corresponding spectra of Phase I strains, for example, NCTC10449.
However, S. mutans JH140 and JH145 did not give good result when used in practice for controlling human dental caries and, by way of example, the following problems arose
(1) S. mutans is highly mutative and is classified into certain strain types. For example, Bratthall classified S. mutans into 5 serotype (a to e) in view of the immunological specificities of the polysaccharides contained in the cell wall (Odont. Revy., 20:143, 1970; ibid. 20:13-27, 1970; and Perch et al, Microbiol. Scand Section B. 82:357, 1974).
Makoto Sato, one of the coinventors of this invention, has classified S. mutans into Human I (HI), Human II (HII) and Rat (R) types with respect to the specific antigens of S. mutans, which respectively correspond to said "`c`, `e` and `f`", "`d` and `g`" and "`a` and `b`" serotypes. has reported
However, BHT-2, the parent strain of JH140 and JH145 are the well known strain of Rat type S. mutans which has never been isolated from humans and which differs from Human type strains. What will happen by administering Rat type strain to humans is not yet entirely clear.
(2) JH140 and JH145 form a large amount of plaque and have a higher ability to adhere than the parent strain. However, it is common knowledge in the art that the formation of plaque and adhesion to the surface of the teeth result in the induction of dental caries.
3. Objects of the Invention
As is well known, S. mutans is highly mutative and has been classified into certain types. However, the competitive relationship between different strain types has not yet been completely clarified. In order to solve this question, we have produced many mutant strains by treating various wild type strains of S. mutans with mutagents such as, for example, nitrogen mustard, nitrosoguanidine or irradiation of ultraviolet rays etc. and have studied their characteristics such as, for example, colonial characteristics, biological characteristics, cariogenic potentials and the like. As a result, we have classified the mutational phases of S. mutans into the following 3 phases in disregard of their strain types